// SPDX-License-Identifier: GPL-2.0-only
/* Kernel thread helper functions.
 *   Copyright (C) 2004 IBM Corporation, Rusty Russell.
 *   Copyright (C) 2009 Red Hat, Inc.
 *
 * Creation is done via kthreadd, so that we get a clean environment
 * even if we're invoked from userspace (think modprobe, hotplug cpu,
 * etc.).
 */
#include <generated/deconfig.h>
#include <uapi/linux/sched/types.h>
#include <linux/mm.h>
#include <linux/mmu_context.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/task.h>
#include <linux/kthread.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/cgroup.h>
#include <linux/cpuset.h>
#include <linux/unistd.h>
#include <linux/file.h>
#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/freezer.h>
#include <linux/ptrace.h>
#include <linux/uaccess.h>
#include <linux/numa.h>
#include <linux/sched/isolation.h>
#include <trace/events/sched.h>


static DEFINE_SPINLOCK(kthread_create_lock);
static LIST_HEAD(kthread_create_list);
struct task_struct *kthreadd_task;

struct kthread_create_info
{
	/* Information passed to kthread() from kthreadd. */
	int (*threadfn)(void *data);
	void *data;
	int node;

	/* Result passed back to kthread_create() from kthreadd. */
	struct task_struct *result;
	struct completion *done;

	struct list_head list;
};

struct kthread {
	unsigned long flags;
	unsigned int cpu;
	int (*threadfn)(void *);
	void *data;
	mm_segment_t oldfs;
	struct completion parked;
	struct completion exited;
#ifdef CONFIG_BLK_CGROUP
	struct cgroup_subsys_state *blkcg_css;
#endif
};

enum KTHREAD_BITS {
	KTHREAD_IS_PER_CPU = 0,
	KTHREAD_SHOULD_STOP,
	KTHREAD_SHOULD_PARK,
};

static inline void set_kthread_struct(void *kthread)
{
	/*
	 * We abuse ->set_child_tid to avoid the new member and because it
	 * can't be wrongly copied by copy_process(). We also rely on fact
	 * that the caller can't exec, so PF_KTHREAD can't be cleared.
	 */
	current->set_child_tid = (__force void __user *)kthread;
}

static inline struct kthread *to_kthread(struct task_struct *k)
{
	WARN_ON(!(k->flags & PF_KTHREAD));
	return (__force void *)k->set_child_tid;
}

void free_kthread_struct(struct task_struct *k)
{
	struct kthread *kthread;

	/*
	 * Can be NULL if this kthread was created by kernel_thread()
	 * or if kmalloc() in kthread() failed.
	 */
	kthread = to_kthread(k);
#ifdef CONFIG_BLK_CGROUP
	WARN_ON_ONCE(kthread && kthread->blkcg_css);
#endif
	kfree(kthread);
}

/**
 * kthread_should_stop - should this kthread return now?
 *
 * When someone calls kthread_stop() on your kthread, it will be woken
 * and this will return true.  You should then return, and your return
 * value will be passed through to kthread_stop().
 */
bool kthread_should_stop(void)
{
	return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
}
EXPORT_SYMBOL(kthread_should_stop);

//bool __kthread_should_park(struct task_struct *k)
//{
//	return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags);
//}
//EXPORT_SYMBOL_GPL(__kthread_should_park);

///**
// * kthread_should_park - should this kthread park now?
// *
// * When someone calls kthread_park() on your kthread, it will be woken
// * and this will return true.  You should then do the necessary
// * cleanup and call kthread_parkme()
// *
// * Similar to kthread_should_stop(), but this keeps the thread alive
// * and in a park position. kthread_unpark() "restarts" the thread and
// * calls the thread function again.
// */
//bool kthread_should_park(void)
//{
//	return __kthread_should_park(current);
//}
//EXPORT_SYMBOL_GPL(kthread_should_park);

///**
// * kthread_freezable_should_stop - should this freezable kthread return now?
// * @was_frozen: optional out parameter, indicates whether %current was frozen
// *
// * kthread_should_stop() for freezable kthreads, which will enter
// * refrigerator if necessary.  This function is safe from kthread_stop() /
// * freezer deadlock and freezable kthreads should use this function instead
// * of calling try_to_freeze() directly.
// */
//bool kthread_freezable_should_stop(bool *was_frozen)
//{
//	bool frozen = false;

//	might_sleep();

//	if (unlikely(freezing(current)))
//		frozen = __refrigerator(true);

//	if (was_frozen)
//		*was_frozen = frozen;

//	return kthread_should_stop();
//}
//EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);

///**
// * kthread_func - return the function specified on kthread creation
// * @task: kthread task in question
// *
// * Returns NULL if the task is not a kthread.
// */
//void *kthread_func(struct task_struct *task)
//{
//	if (task->flags & PF_KTHREAD)
//		return to_kthread(task)->threadfn;
//	return NULL;
//}
//EXPORT_SYMBOL_GPL(kthread_func);

/**
 * kthread_data - return data value specified on kthread creation
 * @task: kthread task in question
 *
 * Return the data value specified when kthread @task was created.
 * The caller is responsible for ensuring the validity of @task when
 * calling this function.
 */
void *kthread_data(struct task_struct *task)
{
	return to_kthread(task)->data;
}
EXPORT_SYMBOL_GPL(kthread_data);

///**
// * kthread_probe_data - speculative version of kthread_data()
// * @task: possible kthread task in question
// *
// * @task could be a kthread task.  Return the data value specified when it
// * was created if accessible.  If @task isn't a kthread task or its data is
// * inaccessible for any reason, %NULL is returned.  This function requires
// * that @task itself is safe to dereference.
// */
//void *kthread_probe_data(struct task_struct *task)
//{
//	struct kthread *kthread = to_kthread(task);
//	void *data = NULL;

//	copy_from_kernel_nofault(&data, &kthread->data, sizeof(data));
//	return data;
//}

//static void __kthread_parkme(struct kthread *self)
//{
//	for (;;) {
//		/*
//		 * TASK_PARKED is a special state; we must serialize against
//		 * possible pending wakeups to avoid store-store collisions on
//		 * task->state.
//		 *
//		 * Such a collision might possibly result in the task state
//		 * changin from TASK_PARKED and us failing the
//		 * wait_task_inactive() in kthread_park().
//		 */
//		set_special_state(TASK_PARKED);
//		if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
//			break;

//		/*
//		 * Thread is going to call schedule(), do not preempt it,
//		 * or the caller of kthread_park() may spend more time in
//		 * wait_task_inactive().
//		 */
//		preempt_disable();
//		complete(&self->parked);
//		schedule_preempt_disabled();
//		preempt_enable();
//	}
//	__set_current_state(TASK_RUNNING);
//}

//void kthread_parkme(void)
//{
//	__kthread_parkme(to_kthread(current));
//}
//EXPORT_SYMBOL_GPL(kthread_parkme);

//static int kthread(void *_create)
//{
//	/* Copy data: it's on kthread's stack */
//	struct kthread_create_info *create = _create;
//	int (*threadfn)(void *data) = create->threadfn;
//	void *data = create->data;
//	struct completion *done;
//	struct kthread *self;
//	int ret;

//	self = kzalloc(sizeof(*self), GFP_KERNEL);
//	set_kthread_struct(self);

//	/* If user was SIGKILLed, I release the structure. */
//	done = xchg(&create->done, NULL);
//	if (!done) {
//		kfree(create);
//		do_exit(-EINTR);
//	}

//	if (!self) {
//		create->result = ERR_PTR(-ENOMEM);
//		complete(done);
//		do_exit(-ENOMEM);
//	}

//	self->threadfn = threadfn;
//	self->data = data;
//	init_completion(&self->exited);
//	init_completion(&self->parked);
//	current->vfork_done = &self->exited;

//	/* OK, tell user we're spawned, wait for stop or wakeup */
//	__set_current_state(TASK_UNINTERRUPTIBLE);
//	create->result = current;
//	/*
//	 * Thread is going to call schedule(), do not preempt it,
//	 * or the creator may spend more time in wait_task_inactive().
//	 */
//	preempt_disable();
//	complete(done);
//	schedule_preempt_disabled();
//	preempt_enable();

//	ret = -EINTR;
//	if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
//		cgroup_kthread_ready();
//		__kthread_parkme(self);
//		ret = threadfn(data);
//	}
//	do_exit(ret);
//}

///* called from do_fork() to get node information for about to be created task */
//int tsk_fork_get_node(struct task_struct *tsk)
//{
//#ifdef CONFIG_NUMA
//	if (tsk == kthreadd_task)
//		return tsk->pref_node_fork;
//#endif
//	return NUMA_NO_NODE;
//}

//static void create_kthread(struct kthread_create_info *create)
//{
//	int pid;

//#ifdef CONFIG_NUMA
//	current->pref_node_fork = create->node;
//#endif
//	/* We want our own signal handler (we take no signals by default). */
//	pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
//	if (pid < 0) {
//		/* If user was SIGKILLed, I release the structure. */
//		struct completion *done = xchg(&create->done, NULL);

//		if (!done) {
//			kfree(create);
//			return;
//		}
//		create->result = ERR_PTR(pid);
//		complete(done);
//	}
//}

//static __printf(4, 0)
//struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
//						    void *data, int node,
//						    const char namefmt[],
//						    va_list args)
//{
//	DECLARE_COMPLETION_ONSTACK(done);
//	struct task_struct *task;
//	struct kthread_create_info *create = kmalloc(sizeof(*create),
//						     GFP_KERNEL);

//	if (!create)
//		return ERR_PTR(-ENOMEM);
//	create->threadfn = threadfn;
//	create->data = data;
//	create->node = node;
//	create->done = &done;

//	spin_lock(&kthread_create_lock);
//	list_add_tail(&create->list, &kthread_create_list);
//	spin_unlock(&kthread_create_lock);

//	wake_up_process(kthreadd_task);
//	/*
//	 * Wait for completion in killable state, for I might be chosen by
//	 * the OOM killer while kthreadd is trying to allocate memory for
//	 * new kernel thread.
//	 */
//	if (unlikely(wait_for_completion_killable(&done))) {
//		/*
//		 * If I was SIGKILLed before kthreadd (or new kernel thread)
//		 * calls complete(), leave the cleanup of this structure to
//		 * that thread.
//		 */
//		if (xchg(&create->done, NULL))
//			return ERR_PTR(-EINTR);
//		/*
//		 * kthreadd (or new kernel thread) will call complete()
//		 * shortly.
//		 */
//		wait_for_completion(&done);
//	}
//	task = create->result;
//	if (!IS_ERR(task)) {
//		static const struct sched_param param = { .sched_priority = 0 };
//		char name[TASK_COMM_LEN];

//		/*
//		 * task is already visible to other tasks, so updating
//		 * COMM must be protected.
//		 */
//		vsnprintf(name, sizeof(name), namefmt, args);
//		set_task_comm(task, name);
//		/*
//		 * root may have changed our (kthreadd's) priority or CPU mask.
//		 * The kernel thread should not inherit these properties.
//		 */
//		sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
//		set_cpus_allowed_ptr(task,
//				     housekeeping_cpumask(HK_FLAG_KTHREAD));
//	}
//	kfree(create);
//	return task;
//}

///**
// * kthread_create_on_node - create a kthread.
// * @threadfn: the function to run until signal_pending(current).
// * @data: data ptr for @threadfn.
// * @node: task and thread structures for the thread are allocated on this node
// * @namefmt: printf-style name for the thread.
// *
// * Description: This helper function creates and names a kernel
// * thread.  The thread will be stopped: use wake_up_process() to start
// * it.  See also kthread_run().  The new thread has SCHED_NORMAL policy and
// * is affine to all CPUs.
// *
// * If thread is going to be bound on a particular cpu, give its node
// * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
// * When woken, the thread will run @threadfn() with @data as its
// * argument. @threadfn() can either call do_exit() directly if it is a
// * standalone thread for which no one will call kthread_stop(), or
// * return when 'kthread_should_stop()' is true (which means
// * kthread_stop() has been called).  The return value should be zero
// * or a negative error number; it will be passed to kthread_stop().
// *
// * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
// */
//struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
//					   void *data, int node,
//					   const char namefmt[],
//					   ...)
//{
//	struct task_struct *task;
//	va_list args;

//	va_start(args, namefmt);
//	task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
//	va_end(args);

//	return task;
//}
//EXPORT_SYMBOL(kthread_create_on_node);

//static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
//{
//	unsigned long flags;

//	if (!wait_task_inactive(p, state)) {
//		WARN_ON(1);
//		return;
//	}

//	/* It's safe because the task is inactive. */
//	raw_spin_lock_irqsave(&p->pi_lock, flags);
//	do_set_cpus_allowed(p, mask);
//	p->flags |= PF_NO_SETAFFINITY;
//	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
//}

//static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
//{
//	__kthread_bind_mask(p, cpumask_of(cpu), state);
//}

//void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
//{
//	__kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
//}

///**
// * kthread_bind - bind a just-created kthread to a cpu.
// * @p: thread created by kthread_create().
// * @cpu: cpu (might not be online, must be possible) for @k to run on.
// *
// * Description: This function is equivalent to set_cpus_allowed(),
// * except that @cpu doesn't need to be online, and the thread must be
// * stopped (i.e., just returned from kthread_create()).
// */
//void kthread_bind(struct task_struct *p, unsigned int cpu)
//{
//	__kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
//}
//EXPORT_SYMBOL(kthread_bind);

///**
// * kthread_create_on_cpu - Create a cpu bound kthread
// * @threadfn: the function to run until signal_pending(current).
// * @data: data ptr for @threadfn.
// * @cpu: The cpu on which the thread should be bound,
// * @namefmt: printf-style name for the thread. Format is restricted
// *	     to "name.*%u". Code fills in cpu number.
// *
// * Description: This helper function creates and names a kernel thread
// */
//struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
//					  void *data, unsigned int cpu,
//					  const char *namefmt)
//{
//	struct task_struct *p;

//	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
//				   cpu);
//	if (IS_ERR(p))
//		return p;
//	kthread_bind(p, cpu);
//	/* CPU hotplug need to bind once again when unparking the thread. */
//	to_kthread(p)->cpu = cpu;
//	return p;
//}

//void kthread_set_per_cpu(struct task_struct *k, int cpu)
//{
//	struct kthread *kthread = to_kthread(k);
//	if (!kthread)
//		return;

//	WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY));

//	if (cpu < 0) {
//		clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
//		return;
//	}

//	kthread->cpu = cpu;
//	set_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
//}

//bool kthread_is_per_cpu(struct task_struct *k)
//{
//	struct kthread *kthread = to_kthread(k);
//	if (!kthread)
//		return false;

//	return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
//}

///**
// * kthread_unpark - unpark a thread created by kthread_create().
// * @k:		thread created by kthread_create().
// *
// * Sets kthread_should_park() for @k to return false, wakes it, and
// * waits for it to return. If the thread is marked percpu then its
// * bound to the cpu again.
// */
//void kthread_unpark(struct task_struct *k)
//{
//	struct kthread *kthread = to_kthread(k);

//	/*
//	 * Newly created kthread was parked when the CPU was offline.
//	 * The binding was lost and we need to set it again.
//	 */
//	if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
//		__kthread_bind(k, kthread->cpu, TASK_PARKED);

//	clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
//	/*
//	 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
//	 */
//	wake_up_state(k, TASK_PARKED);
//}
//EXPORT_SYMBOL_GPL(kthread_unpark);

///**
// * kthread_park - park a thread created by kthread_create().
// * @k: thread created by kthread_create().
// *
// * Sets kthread_should_park() for @k to return true, wakes it, and
// * waits for it to return. This can also be called after kthread_create()
// * instead of calling wake_up_process(): the thread will park without
// * calling threadfn().
// *
// * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
// * If called by the kthread itself just the park bit is set.
// */
//int kthread_park(struct task_struct *k)
//{
//	struct kthread *kthread = to_kthread(k);

//	if (WARN_ON(k->flags & PF_EXITING))
//		return -ENOSYS;

//	if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
//		return -EBUSY;

//	set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
//	if (k != current) {
//		wake_up_process(k);
//		/*
//		 * Wait for __kthread_parkme() to complete(), this means we
//		 * _will_ have TASK_PARKED and are about to call schedule().
//		 */
//		wait_for_completion(&kthread->parked);
//		/*
//		 * Now wait for that schedule() to complete and the task to
//		 * get scheduled out.
//		 */
//		WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
//	}

//	return 0;
//}
//EXPORT_SYMBOL_GPL(kthread_park);

///**
// * kthread_stop - stop a thread created by kthread_create().
// * @k: thread created by kthread_create().
// *
// * Sets kthread_should_stop() for @k to return true, wakes it, and
// * waits for it to exit. This can also be called after kthread_create()
// * instead of calling wake_up_process(): the thread will exit without
// * calling threadfn().
// *
// * If threadfn() may call do_exit() itself, the caller must ensure
// * task_struct can't go away.
// *
// * Returns the result of threadfn(), or %-EINTR if wake_up_process()
// * was never called.
// */
//int kthread_stop(struct task_struct *k)
//{
//	struct kthread *kthread;
//	int ret;

//	trace_sched_kthread_stop(k);

//	get_task_struct(k);
//	kthread = to_kthread(k);
//	set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
//	kthread_unpark(k);
//	wake_up_process(k);
//	wait_for_completion(&kthread->exited);
//	ret = k->exit_code;
//	put_task_struct(k);

//	trace_sched_kthread_stop_ret(ret);
//	return ret;
//}
//EXPORT_SYMBOL(kthread_stop);

//int kthreadd(void *unused)
//{
//	struct task_struct *tsk = current;

//	/* Setup a clean context for our children to inherit. */
//	set_task_comm(tsk, "kthreadd");
//	ignore_signals(tsk);
//	set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_FLAG_KTHREAD));
//	set_mems_allowed(node_states[N_MEMORY]);

//	current->flags |= PF_NOFREEZE;
//	cgroup_init_kthreadd();

//	for (;;) {
//		set_current_state(TASK_INTERRUPTIBLE);
//		if (list_empty(&kthread_create_list))
//			schedule();
//		__set_current_state(TASK_RUNNING);

//		spin_lock(&kthread_create_lock);
//		while (!list_empty(&kthread_create_list)) {
//			struct kthread_create_info *create;

//			create = list_entry(kthread_create_list.next,
//					    struct kthread_create_info, list);
//			list_del_init(&create->list);
//			spin_unlock(&kthread_create_lock);

//			create_kthread(create);

//			spin_lock(&kthread_create_lock);
//		}
//		spin_unlock(&kthread_create_lock);
//	}

//	return 0;
//}

//void __kthread_init_worker(struct kthread_worker *worker,
//				const char *name,
//				struct lock_class_key *key)
//{
//	memset(worker, 0, sizeof(struct kthread_worker));
//	raw_spin_lock_init(&worker->lock);
//	lockdep_set_class_and_name(&worker->lock, key, name);
//	INIT_LIST_HEAD(&worker->work_list);
//	INIT_LIST_HEAD(&worker->delayed_work_list);
//}
//EXPORT_SYMBOL_GPL(__kthread_init_worker);

///**
// * kthread_worker_fn - kthread function to process kthread_worker
// * @worker_ptr: pointer to initialized kthread_worker
// *
// * This function implements the main cycle of kthread worker. It processes
// * work_list until it is stopped with kthread_stop(). It sleeps when the queue
// * is empty.
// *
// * The works are not allowed to keep any locks, disable preemption or interrupts
// * when they finish. There is defined a safe point for freezing when one work
// * finishes and before a new one is started.
// *
// * Also the works must not be handled by more than one worker at the same time,
// * see also kthread_queue_work().
// */
//int kthread_worker_fn(void *worker_ptr)
//{
//	struct kthread_worker *worker = worker_ptr;
//	struct kthread_work *work;

//	/*
//	 * FIXME: Update the check and remove the assignment when all kthread
//	 * worker users are created using kthread_create_worker*() functions.
//	 */
//	WARN_ON(worker->task && worker->task != current);
//	worker->task = current;

//	if (worker->flags & KTW_FREEZABLE)
//		set_freezable();

//repeat:
//	set_current_state(TASK_INTERRUPTIBLE);	/* mb paired w/ kthread_stop */

//	if (kthread_should_stop()) {
//		__set_current_state(TASK_RUNNING);
//		raw_spin_lock_irq(&worker->lock);
//		worker->task = NULL;
//		raw_spin_unlock_irq(&worker->lock);
//		return 0;
//	}

//	work = NULL;
//	raw_spin_lock_irq(&worker->lock);
//	if (!list_empty(&worker->work_list)) {
//		work = list_first_entry(&worker->work_list,
//					struct kthread_work, node);
//		list_del_init(&work->node);
//	}
//	worker->current_work = work;
//	raw_spin_unlock_irq(&worker->lock);

//	if (work) {
//		__set_current_state(TASK_RUNNING);
//		work->func(work);
//	} else if (!freezing(current))
//		schedule();

//	try_to_freeze();
//	cond_resched();
//	goto repeat;
//}
//EXPORT_SYMBOL_GPL(kthread_worker_fn);

//static __printf(3, 0) struct kthread_worker *
//__kthread_create_worker(int cpu, unsigned int flags,
//			const char namefmt[], va_list args)
//{
//	struct kthread_worker *worker;
//	struct task_struct *task;
//	int node = NUMA_NO_NODE;

//	worker = kzalloc(sizeof(*worker), GFP_KERNEL);
//	if (!worker)
//		return ERR_PTR(-ENOMEM);

//	kthread_init_worker(worker);

//	if (cpu >= 0)
//		node = cpu_to_node(cpu);

//	task = __kthread_create_on_node(kthread_worker_fn, worker,
//						node, namefmt, args);
//	if (IS_ERR(task))
//		goto fail_task;

//	if (cpu >= 0)
//		kthread_bind(task, cpu);

//	worker->flags = flags;
//	worker->task = task;
//	wake_up_process(task);
//	return worker;

//fail_task:
//	kfree(worker);
//	return ERR_CAST(task);
//}

///**
// * kthread_create_worker - create a kthread worker
// * @flags: flags modifying the default behavior of the worker
// * @namefmt: printf-style name for the kthread worker (task).
// *
// * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
// * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
// * when the worker was SIGKILLed.
// */
//struct kthread_worker *
//kthread_create_worker(unsigned int flags, const char namefmt[], ...)
//{
//	struct kthread_worker *worker;
//	va_list args;

//	va_start(args, namefmt);
//	worker = __kthread_create_worker(-1, flags, namefmt, args);
//	va_end(args);

//	return worker;
//}
//EXPORT_SYMBOL(kthread_create_worker);

///**
// * kthread_create_worker_on_cpu - create a kthread worker and bind it
// *	to a given CPU and the associated NUMA node.
// * @cpu: CPU number
// * @flags: flags modifying the default behavior of the worker
// * @namefmt: printf-style name for the kthread worker (task).
// *
// * Use a valid CPU number if you want to bind the kthread worker
// * to the given CPU and the associated NUMA node.
// *
// * A good practice is to add the cpu number also into the worker name.
// * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
// *
// * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
// * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
// * when the worker was SIGKILLed.
// */
//struct kthread_worker *
//kthread_create_worker_on_cpu(int cpu, unsigned int flags,
//			     const char namefmt[], ...)
//{
//	struct kthread_worker *worker;
//	va_list args;

//	va_start(args, namefmt);
//	worker = __kthread_create_worker(cpu, flags, namefmt, args);
//	va_end(args);

//	return worker;
//}
//EXPORT_SYMBOL(kthread_create_worker_on_cpu);

///*
// * Returns true when the work could not be queued at the moment.
// * It happens when it is already pending in a worker list
// * or when it is being cancelled.
// */
//static inline bool queuing_blocked(struct kthread_worker *worker,
//				   struct kthread_work *work)
//{
//	lockdep_assert_held(&worker->lock);

//	return !list_empty(&work->node) || work->canceling;
//}

//static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
//					     struct kthread_work *work)
//{
//	lockdep_assert_held(&worker->lock);
//	WARN_ON_ONCE(!list_empty(&work->node));
//	/* Do not use a work with >1 worker, see kthread_queue_work() */
//	WARN_ON_ONCE(work->worker && work->worker != worker);
//}

///* insert @work before @pos in @worker */
//static void kthread_insert_work(struct kthread_worker *worker,
//				struct kthread_work *work,
//				struct list_head *pos)
//{
//	kthread_insert_work_sanity_check(worker, work);

//	list_add_tail(&work->node, pos);
//	work->worker = worker;
//	if (!worker->current_work && likely(worker->task))
//		wake_up_process(worker->task);
//}

///**
// * kthread_queue_work - queue a kthread_work
// * @worker: target kthread_worker
// * @work: kthread_work to queue
// *
// * Queue @work to work processor @task for async execution.  @task
// * must have been created with kthread_worker_create().  Returns %true
// * if @work was successfully queued, %false if it was already pending.
// *
// * Reinitialize the work if it needs to be used by another worker.
// * For example, when the worker was stopped and started again.
// */
//bool kthread_queue_work(struct kthread_worker *worker,
//			struct kthread_work *work)
//{
//	bool ret = false;
//	unsigned long flags;

//	raw_spin_lock_irqsave(&worker->lock, flags);
//	if (!queuing_blocked(worker, work)) {
//		kthread_insert_work(worker, work, &worker->work_list);
//		ret = true;
//	}
//	raw_spin_unlock_irqrestore(&worker->lock, flags);
//	return ret;
//}
//EXPORT_SYMBOL_GPL(kthread_queue_work);

///**
// * kthread_delayed_work_timer_fn - callback that queues the associated kthread
// *	delayed work when the timer expires.
// * @t: pointer to the expired timer
// *
// * The format of the function is defined by struct timer_list.
// * It should have been called from irqsafe timer with irq already off.
// */
//void kthread_delayed_work_timer_fn(struct timer_list *t)
//{
//	struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
//	struct kthread_work *work = &dwork->work;
//	struct kthread_worker *worker = work->worker;
//	unsigned long flags;

//	/*
//	 * This might happen when a pending work is reinitialized.
//	 * It means that it is used a wrong way.
//	 */
//	if (WARN_ON_ONCE(!worker))
//		return;

//	raw_spin_lock_irqsave(&worker->lock, flags);
//	/* Work must not be used with >1 worker, see kthread_queue_work(). */
//	WARN_ON_ONCE(work->worker != worker);

//	/* Move the work from worker->delayed_work_list. */
//	WARN_ON_ONCE(list_empty(&work->node));
//	list_del_init(&work->node);
//	if (!work->canceling)
//		kthread_insert_work(worker, work, &worker->work_list);

//	raw_spin_unlock_irqrestore(&worker->lock, flags);
//}
//EXPORT_SYMBOL(kthread_delayed_work_timer_fn);

//static void __kthread_queue_delayed_work(struct kthread_worker *worker,
//					 struct kthread_delayed_work *dwork,
//					 unsigned long delay)
//{
//	struct timer_list *timer = &dwork->timer;
//	struct kthread_work *work = &dwork->work;

//	WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);

//	/*
//	 * If @delay is 0, queue @dwork->work immediately.  This is for
//	 * both optimization and correctness.  The earliest @timer can
//	 * expire is on the closest next tick and delayed_work users depend
//	 * on that there's no such delay when @delay is 0.
//	 */
//	if (!delay) {
//		kthread_insert_work(worker, work, &worker->work_list);
//		return;
//	}

//	/* Be paranoid and try to detect possible races already now. */
//	kthread_insert_work_sanity_check(worker, work);

//	list_add(&work->node, &worker->delayed_work_list);
//	work->worker = worker;
//	timer->expires = jiffies + delay;
//	add_timer(timer);
//}

///**
// * kthread_queue_delayed_work - queue the associated kthread work
// *	after a delay.
// * @worker: target kthread_worker
// * @dwork: kthread_delayed_work to queue
// * @delay: number of jiffies to wait before queuing
// *
// * If the work has not been pending it starts a timer that will queue
// * the work after the given @delay. If @delay is zero, it queues the
// * work immediately.
// *
// * Return: %false if the @work has already been pending. It means that
// * either the timer was running or the work was queued. It returns %true
// * otherwise.
// */
//bool kthread_queue_delayed_work(struct kthread_worker *worker,
//				struct kthread_delayed_work *dwork,
//				unsigned long delay)
//{
//	struct kthread_work *work = &dwork->work;
//	unsigned long flags;
//	bool ret = false;

//	raw_spin_lock_irqsave(&worker->lock, flags);

//	if (!queuing_blocked(worker, work)) {
//		__kthread_queue_delayed_work(worker, dwork, delay);
//		ret = true;
//	}

//	raw_spin_unlock_irqrestore(&worker->lock, flags);
//	return ret;
//}
//EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);

//struct kthread_flush_work {
//	struct kthread_work	work;
//	struct completion	done;
//};

//static void kthread_flush_work_fn(struct kthread_work *work)
//{
//	struct kthread_flush_work *fwork =
//		container_of(work, struct kthread_flush_work, work);
//	complete(&fwork->done);
//}

///**
// * kthread_flush_work - flush a kthread_work
// * @work: work to flush
// *
// * If @work is queued or executing, wait for it to finish execution.
// */
//void kthread_flush_work(struct kthread_work *work)
//{
//	struct kthread_flush_work fwork = {
//		KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
//		COMPLETION_INITIALIZER_ONSTACK(fwork.done),
//	};
//	struct kthread_worker *worker;
//	bool noop = false;

//	worker = work->worker;
//	if (!worker)
//		return;

//	raw_spin_lock_irq(&worker->lock);
//	/* Work must not be used with >1 worker, see kthread_queue_work(). */
//	WARN_ON_ONCE(work->worker != worker);

//	if (!list_empty(&work->node))
//		kthread_insert_work(worker, &fwork.work, work->node.next);
//	else if (worker->current_work == work)
//		kthread_insert_work(worker, &fwork.work,
//				    worker->work_list.next);
//	else
//		noop = true;

//	raw_spin_unlock_irq(&worker->lock);

//	if (!noop)
//		wait_for_completion(&fwork.done);
//}
//EXPORT_SYMBOL_GPL(kthread_flush_work);

///*
// * Make sure that the timer is neither set nor running and could
// * not manipulate the work list_head any longer.
// *
// * The function is called under worker->lock. The lock is temporary
// * released but the timer can't be set again in the meantime.
// */
//static void kthread_cancel_delayed_work_timer(struct kthread_work *work,
//					      unsigned long *flags)
//{
//	struct kthread_delayed_work *dwork =
//		container_of(work, struct kthread_delayed_work, work);
//	struct kthread_worker *worker = work->worker;

//	/*
//	 * del_timer_sync() must be called to make sure that the timer
//	 * callback is not running. The lock must be temporary released
//	 * to avoid a deadlock with the callback. In the meantime,
//	 * any queuing is blocked by setting the canceling counter.
//	 */
//	work->canceling++;
//	raw_spin_unlock_irqrestore(&worker->lock, *flags);
//	del_timer_sync(&dwork->timer);
//	raw_spin_lock_irqsave(&worker->lock, *flags);
//	work->canceling--;
//}

///*
// * This function removes the work from the worker queue.
// *
// * It is called under worker->lock. The caller must make sure that
// * the timer used by delayed work is not running, e.g. by calling
// * kthread_cancel_delayed_work_timer().
// *
// * The work might still be in use when this function finishes. See the
// * current_work proceed by the worker.
// *
// * Return: %true if @work was pending and successfully canceled,
// *	%false if @work was not pending
// */
//static bool __kthread_cancel_work(struct kthread_work *work)
//{
//	/*
//	 * Try to remove the work from a worker list. It might either
//	 * be from worker->work_list or from worker->delayed_work_list.
//	 */
//	if (!list_empty(&work->node)) {
//		list_del_init(&work->node);
//		return true;
//	}

//	return false;
//}

///**
// * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
// * @worker: kthread worker to use
// * @dwork: kthread delayed work to queue
// * @delay: number of jiffies to wait before queuing
// *
// * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
// * modify @dwork's timer so that it expires after @delay. If @delay is zero,
// * @work is guaranteed to be queued immediately.
// *
// * Return: %true if @dwork was pending and its timer was modified,
// * %false otherwise.
// *
// * A special case is when the work is being canceled in parallel.
// * It might be caused either by the real kthread_cancel_delayed_work_sync()
// * or yet another kthread_mod_delayed_work() call. We let the other command
// * win and return %false here. The caller is supposed to synchronize these
// * operations a reasonable way.
// *
// * This function is safe to call from any context including IRQ handler.
// * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
// * for details.
// */
//bool kthread_mod_delayed_work(struct kthread_worker *worker,
//			      struct kthread_delayed_work *dwork,
//			      unsigned long delay)
//{
//	struct kthread_work *work = &dwork->work;
//	unsigned long flags;
//	int ret = false;

//	raw_spin_lock_irqsave(&worker->lock, flags);

//	/* Do not bother with canceling when never queued. */
//	if (!work->worker)
//		goto fast_queue;

//	/* Work must not be used with >1 worker, see kthread_queue_work() */
//	WARN_ON_ONCE(work->worker != worker);

//	/*
//	 * Temporary cancel the work but do not fight with another command
//	 * that is canceling the work as well.
//	 *
//	 * It is a bit tricky because of possible races with another
//	 * mod_delayed_work() and cancel_delayed_work() callers.
//	 *
//	 * The timer must be canceled first because worker->lock is released
//	 * when doing so. But the work can be removed from the queue (list)
//	 * only when it can be queued again so that the return value can
//	 * be used for reference counting.
//	 */
//	kthread_cancel_delayed_work_timer(work, &flags);
//	if (work->canceling)
//		goto out;
//	ret = __kthread_cancel_work(work);

//fast_queue:
//	__kthread_queue_delayed_work(worker, dwork, delay);
//out:
//	raw_spin_unlock_irqrestore(&worker->lock, flags);
//	return ret;
//}
//EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);

//static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
//{
//	struct kthread_worker *worker = work->worker;
//	unsigned long flags;
//	int ret = false;

//	if (!worker)
//		goto out;

//	raw_spin_lock_irqsave(&worker->lock, flags);
//	/* Work must not be used with >1 worker, see kthread_queue_work(). */
//	WARN_ON_ONCE(work->worker != worker);

//	if (is_dwork)
//		kthread_cancel_delayed_work_timer(work, &flags);

//	ret = __kthread_cancel_work(work);

//	if (worker->current_work != work)
//		goto out_fast;

//	/*
//	 * The work is in progress and we need to wait with the lock released.
//	 * In the meantime, block any queuing by setting the canceling counter.
//	 */
//	work->canceling++;
//	raw_spin_unlock_irqrestore(&worker->lock, flags);
//	kthread_flush_work(work);
//	raw_spin_lock_irqsave(&worker->lock, flags);
//	work->canceling--;

//out_fast:
//	raw_spin_unlock_irqrestore(&worker->lock, flags);
//out:
//	return ret;
//}

///**
// * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
// * @work: the kthread work to cancel
// *
// * Cancel @work and wait for its execution to finish.  This function
// * can be used even if the work re-queues itself. On return from this
// * function, @work is guaranteed to be not pending or executing on any CPU.
// *
// * kthread_cancel_work_sync(&delayed_work->work) must not be used for
// * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
// *
// * The caller must ensure that the worker on which @work was last
// * queued can't be destroyed before this function returns.
// *
// * Return: %true if @work was pending, %false otherwise.
// */
//bool kthread_cancel_work_sync(struct kthread_work *work)
//{
//	return __kthread_cancel_work_sync(work, false);
//}
//EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);

///**
// * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
// *	wait for it to finish.
// * @dwork: the kthread delayed work to cancel
// *
// * This is kthread_cancel_work_sync() for delayed works.
// *
// * Return: %true if @dwork was pending, %false otherwise.
// */
//bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
//{
//	return __kthread_cancel_work_sync(&dwork->work, true);
//}
//EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);

///**
// * kthread_flush_worker - flush all current works on a kthread_worker
// * @worker: worker to flush
// *
// * Wait until all currently executing or pending works on @worker are
// * finished.
// */
//void kthread_flush_worker(struct kthread_worker *worker)
//{
//	struct kthread_flush_work fwork = {
//		KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
//		COMPLETION_INITIALIZER_ONSTACK(fwork.done),
//	};

//	kthread_queue_work(worker, &fwork.work);
//	wait_for_completion(&fwork.done);
//}
//EXPORT_SYMBOL_GPL(kthread_flush_worker);

///**
// * kthread_destroy_worker - destroy a kthread worker
// * @worker: worker to be destroyed
// *
// * Flush and destroy @worker.  The simple flush is enough because the kthread
// * worker API is used only in trivial scenarios.  There are no multi-step state
// * machines needed.
// */
//void kthread_destroy_worker(struct kthread_worker *worker)
//{
//	struct task_struct *task;

//	task = worker->task;
//	if (WARN_ON(!task))
//		return;

//	kthread_flush_worker(worker);
//	kthread_stop(task);
//	WARN_ON(!list_empty(&worker->work_list));
//	kfree(worker);
//}
//EXPORT_SYMBOL(kthread_destroy_worker);

///**
// * kthread_use_mm - make the calling kthread operate on an address space
// * @mm: address space to operate on
// */
//void kthread_use_mm(struct mm_struct *mm)
//{
//	struct mm_struct *active_mm;
//	struct task_struct *tsk = current;

//	WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
//	WARN_ON_ONCE(tsk->mm);

//	task_lock(tsk);
//	/* Hold off tlb flush IPIs while switching mm's */
//	local_irq_disable();
//	active_mm = tsk->active_mm;
//	if (active_mm != mm) {
//		mmgrab(mm);
//		tsk->active_mm = mm;
//	}
//	tsk->mm = mm;
//	switch_mm_irqs_off(active_mm, mm, tsk);
//	local_irq_enable();
//	task_unlock(tsk);
//#ifdef finish_arch_post_lock_switch
//	finish_arch_post_lock_switch();
//#endif

//	if (active_mm != mm)
//		mmdrop(active_mm);

//	to_kthread(tsk)->oldfs = force_uaccess_begin();
//}
//EXPORT_SYMBOL_GPL(kthread_use_mm);

///**
// * kthread_unuse_mm - reverse the effect of kthread_use_mm()
// * @mm: address space to operate on
// */
//void kthread_unuse_mm(struct mm_struct *mm)
//{
//	struct task_struct *tsk = current;

//	WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
//	WARN_ON_ONCE(!tsk->mm);

//	force_uaccess_end(to_kthread(tsk)->oldfs);

//	task_lock(tsk);
//	sync_mm_rss(mm);
//	local_irq_disable();
//	tsk->mm = NULL;
//	/* active_mm is still 'mm' */
//	enter_lazy_tlb(mm, tsk);
//	local_irq_enable();
//	task_unlock(tsk);
//}
//EXPORT_SYMBOL_GPL(kthread_unuse_mm);

//#ifdef CONFIG_BLK_CGROUP
///**
// * kthread_associate_blkcg - associate blkcg to current kthread
// * @css: the cgroup info
// *
// * Current thread must be a kthread. The thread is running jobs on behalf of
// * other threads. In some cases, we expect the jobs attach cgroup info of
// * original threads instead of that of current thread. This function stores
// * original thread's cgroup info in current kthread context for later
// * retrieval.
// */
//void kthread_associate_blkcg(struct cgroup_subsys_state *css)
//{
//	struct kthread *kthread;

//	if (!(current->flags & PF_KTHREAD))
//		return;
//	kthread = to_kthread(current);
//	if (!kthread)
//		return;

//	if (kthread->blkcg_css) {
//		css_put(kthread->blkcg_css);
//		kthread->blkcg_css = NULL;
//	}
//	if (css) {
//		css_get(css);
//		kthread->blkcg_css = css;
//	}
//}
//EXPORT_SYMBOL(kthread_associate_blkcg);

///**
// * kthread_blkcg - get associated blkcg css of current kthread
// *
// * Current thread must be a kthread.
// */
//struct cgroup_subsys_state *kthread_blkcg(void)
//{
//	struct kthread *kthread;

//	if (current->flags & PF_KTHREAD) {
//		kthread = to_kthread(current);
//		if (kthread)
//			return kthread->blkcg_css;
//	}
//	return NULL;
//}
//EXPORT_SYMBOL(kthread_blkcg);
//#endif
